<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes" />
    <title>ShellCheck: SC2299 – Parameter expansions can't be nested. Use temporary variables.</title>
    <link rel="stylesheet" href="css/bootstrap.min.css" />
  </head>
  <body style="margin-left: auto; margin-right: auto; max-width: 800px">
    <h1>SC2299 – ShellCheck Wiki</h1>
    <a href="https://github.com/koalaman/shellcheck/wiki/SC2299">See this page on GitHub</a>
    <p style="display: none"><a href="index.html">Sitemap</a></p>
    <hr />
    <h2
id="parameter-expansions-cant-be-nested-use-temporary-variables">Parameter
expansions can't be nested. Use temporary variables.</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2299.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="va">path</span><span class="op">=</span><span class="st">&quot;/path/to/MyFile.mp3&quot;</span></span>
<span id="cb1-2"><a href="SC2299.html#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="bu">echo</span> <span class="st">&quot;Playing </span><span class="va">${$</span><span class="er">{path##*/</span><span class="va">}</span><span class="st">%.*}&quot;</span>    <span class="co"># Expect: Playing MyFile</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2299.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="va">path</span><span class="op">=</span><span class="st">&quot;/path/to/MyFile.mp3&quot;</span></span>
<span id="cb2-2"><a href="SC2299.html#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="va">tmp</span><span class="op">=</span><span class="va">${path</span><span class="op">##</span><span class="pp">*</span>/<span class="va">}</span></span>
<span id="cb2-3"><a href="SC2299.html#cb2-3" aria-hidden="true" tabindex="-1"></a><span class="bu">echo</span> <span class="st">&quot;Playing </span><span class="va">${tmp</span><span class="op">%</span>.<span class="pp">*</span><span class="va">}</span><span class="st">&quot;</span></span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>ShellCheck found what appears to be a nested parameter expansion. In
the example, it was hoping to combine <code>${var##*/}</code> to strip
the directory and <code>${var%.*}</code> to strip the extension.</p>
<p>Parameter expansions can't be nested. Use temporary variables
instead, so that each parameter expansion only does a single
operation.</p>
<p>Alternatively, if the goal is to dynamically generate and expand a
variable name, see <a href="SC2082.html">SC2082</a>.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>None</p>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
</ul>
    <hr />
    <p style='font-size: 80%'><a href="../index.html">ShellCheck</a> is a static analysis tool for shell scripts. This page is part of its documentation.</p>
  </body>
</html>


